How to stop water leaking through my tile grout joints?


I have 2x2 inch mosaic tile in a handicap shower I am having trouble with water seeping through the tile grout an leaking in the crawl space below. What would be the best way to seal the grout? Thank you for your answer


ANSWER - If water from your shower is leaking into a crawl space the problem is not the cementitious grout joints.  There has to be an underlying problem with the shower pan's waterproof membrane.  It likely was not installed correctly.

To waterproof a shower pan and shower walls, you have to have a waterproof membrane that meets ANSI A118.10 to be properly installed.  The plumbing code says that the waterproof shower pan liner has to extend up at least 3 inches above the height of the top surface of the dam/curb.  Along with having a moisture barrier sheeting behind the wall substrate so it weather laps over the shower pan liner.

Apparently your waterproof membrane is not working as it should or you wouldn't have a leak into the crawl space.   The proper way to fix this problem is to remove at least the shower pan and reinstall it correctly.

If you have a limited budget and want to take a risk, there is a possible fix that doesn't meet the standards.  You could remove the cementitious grout from the grout joints, remove the grout in the shower pan floor to wall horizontal transitions, and remove the grout in the inside corners of the wall tile.

The once the joints are open and clean, use an ASTM C920 silione sealant and fill all of those joints.   If your 2x2 inch tile is porcelain and you have these grout joints filled with sealant, in theory, if you do everything correctly, water should not be able to pass through.  You might have to do the same thing with all of the grout joints on the wall tile.

This method doesn't come with a guarantee and only proceed at your own risk.

40 thoughts on “How to stop water leaking through my tile grout joints?

  1. Dave Anderson says:

    It’s nice to know how my shower grout leak will be fixed, but I don’t know how to repair or replace it. I think I am going to call a grout repairman and have them come to fix it now that I know what the problem might be. I want this grout problem fixed effectively.

    • Donato Pompo says:

      It isn’t a grout problem. It is a waterproof problem. The grout problem is a symptom of the waterproof problem.

  2. Leslie says:

    I have a small backsplash in a bathroom to grout. If I put a thin layer of caulking on before I grout, will the grout still breath, dry out, and not mould if it gets wet? Or will the calking behind the grout mould?

    • Donato Pompo says:

      If you use a quality caulking/sealant per industry standards would be an ASTM C920 sealant such as a 100% silicone sealant it should keep water out. Grouting over the sealant with a cementitious grout wouldn’t be recommended as it may not perform well and it will limit the performance of the sealant. I would grout the entire grout joint with the silicone sealant.

      Use blue masking tape along the edges of the tile before applying the sealant. After applying the sealant pull of the masking tape right away otherwise it can be problematic.

  3. M Lynn Cooper says:

    I have a leak coming into my tile shower. My home is new and the plumber and the tile expert cannot explain what or why it is leaking. The leak is on a non-plumbing wall and only leaks after my shower has been in use. The leak is located on the floor next to a bench seat . Help!

    • Donato Pompo says:

      You know that the leak is caused by using the shower. The question is what is the source of the leak and where is it located. If you know that, then you can determine how to remediate it.

      The source of a leak is often not where the the water leak exits. It could be due to a plumbing pipe even if the leak is adjacent to a non-plumbing wall. You know that the leak only occurs when the water is on, so that means it isn’t a leaking pipe. If it is the plumbing it is occurring where the water is coming out at the values.

      Often we find that a shower bench has not be properly waterproofed or sloped. If that is the case then water can be entering though the tile grout joints and transitions joints and leaking into the bench and then out of the bench. The bench should have been fully waterproofed and sloped a 1/4″ per foot towards the drain. The only way to determine if it was constructed correctly is to forensically remove certain tiles to see how it was constructed.

  4. Thanh says:

    I have tub with a shower. It seems to be leaking down to the basement on far end away from the plumbing. I filled tub; it doesn’t leak. In the process of filling tub I used the faucet and didn’t notice leak. I let shower run without anyone inside and didn’t notice leak. I sprayed the shower wall close to shower head side and noticed a leak but it came down on another location in basement. Why the difference in leak location? More than one leak source? Could the leak run down the sliding glass door and down basement?

    • Donato Pompo says:

      That is the challenge with water leaks that where the leak shows up can be no where near where the water source is located.

      Generally speaking in a bathtub the areas most likely to allow water to leak out is at the tub transpositions. That can be from the tub to the walls or at the windows or at glass partitions. So you should clean those transitions and caulk them with an ASTM C920 sealant like a pure silicone or polyurethane. Try that and see if it works.

  5. CJndy VH says:

    There is a small crack in one of the tiles near the shower door. I think there is a leak since I see water damage in the ceiling below our shower. Can I caulk it to stop the leak or do I need to have a Plummer come and remove all the tile to repair it?

    • Donato Pompo says:

      The crack is a symptom of a problem and the leaking maybe collateral damage from the crack. If the crack is inside the shower that is a bigger problem because there should be a waterproof membrane under the tile floor and it should not cause a leak. If the crack tile is outside the shower that doesn’t mean that is where water is getting into or ending up on the ceiling below.

      You could temporarily caulk the crack and see what happens, but ultimately if the leak is getting to the ceiling down below the shower it could be a bigger problem. Water getting to drywall and inside the ceiling cavity could develop microbial growth (mold) and as long as it stays wet and has that organic food it can grow. You might need to have water loss restoration company come investigate it. You also might need to file a claim with your home insurance as they might cover the repair of the damages.

  6. William Kaye says:

    I have a marble shower. Recently notices water oozing up through floor grout lines. Grout/sealer around periphery rapidly becoming moldy. Foul smell. 10 years ago shower did same thing plus leak to the ceiling below. We hired a high end professional through the insurance company. This time no leak to the celing below just above mentioned features.

    • Donato Pompo says:

      If water is oozing up through the grout joints and it is becoming moldy then water is not able to drain away. It appears you have some sort of leak. Maybe a plumbing leak or maybe the drain is restricted in the shower and water is not allowed to fully drain away. I would file a claim with your insurance and say you think you have a plumbing leak and have them come out and investigate. They will determine if it is a valid claim or not, but they might give you an idea of what the cause is and then you can get it repaired or do more investigating.

  7. Juliet Segee says:

    I’m out of my depth here and need advice. I noticed a milky white stain popped up on the metal part of my shower drain. Then I noticed standing water on the tile near the milky spot. When I sqeegy the water away, more water seeps in from below through the grout. This home was constructed 9/18, 1yr warranty on the shower. What do you think the problem is and what type of contractor should I call to diagnose and fix the problem?

    • Donato Pompo says:

      The white color is likely calcium minerals. When the moisture evaporates it precipitates the minerals and becomes efflorescence staining. Since the shower floor should be waterproofed, chances are that when they installed the tile they didn’t protect the weep holes in the bottom of the drain so water could drain out. So when you use the shower it saturates the underlying materials until it has a chance to evaporate. If you take showers frequently it might never dry out.

      The only way to verify that is the problem and fix it is to remove tiles around the drain and expose the bottom of it to verify and correct.

  8. Kaycee says:

    My shower is leaking through the grout on fixture side where the tile and tub meet. I removed grout and re grouted. A month later it is happening again. Tile was done in 2013 started leaking about 6 months ago. I had prepped the shower and used Kerdi membrane behind it. I did not do the tiling myself. Will I have to remove the bottom tile and look at the membrane? Not sure what could have happened.

    • Donato Pompo says:

      The problem is that the transition joint from the tub to the wall tile should not be grouted with a grout. It should be filled with an ASTM C920 sealant (caulking) that is typically a 100% silicone sealant or a polyurethane sealant.

      First remove the grout and clean the tube and tile surfaces to remove all residuals and contaminates. Put in a round closed cell foam backup strip and make sure you allow at least 1/4″ space for the sealant. Tape both sides of the joint with good green or blue masking tape. Fill the joint and tool it to a slight concave shape. Immediately pull the masking tape away from the joint. If you wait too long it will pull the sealant out.

      So as long as that joint is where the water is coming in at and if you have caulked it correctly with the correct sealant, it should stop the leak.

  9. Fabian Hernandez says:

    Part of the grout on the shower floor has chipped off between a couple of tiles and now there is water between the floor tile and the shower liner/pan. How do I drain/absorb the water between the floor tile and the shower liner/pan? Do I need to remove the floor tile, dry the pan, and lay down new floor tile and re-grout?

    • Donato Pompo says:

      The first question to figure out is why did the grout come loose. Either it wasn’t installed correctly or there is excessive movement in the floor or there are not adequate movement joints.

      Sounds like the tile was bonded directly to the waterproof shower pan liner/membrane. If so the question is whether there is an adequate slope on the membrane so water will travel to the drain weep holes.

      The standards and building code is there should be a slope of 1/4″ per foot towards the drain. Also the drain weep holes should be protected with a plastic weep hole protector or with pea gravel so water can readily drain through them.

      A shower floor with cementitious grout will absorb water and the grout and thin-set will become saturated with water after a certain degree of use. That is normal and if the tile is bonded to a waterproof membrane it will dry out fairly fast.

  10. Gracie says:

    We had our shower remodel about 10 years ago, and now it has begun to leak though the ceiling into our hall below. It appear that the grout around the entire floor edges of the shower may be loose. Should we remove and replace the old grout ourselves or should we do something else.

    • Donato Pompo says:

      Even if all of the grout was missing around the perimeter of the shower floor it still should not leak. The fact that it is leaking indicates it was not properly waterproofed.

      Even if you removed all of the perimeter grout and filled that joint with an ASTM C920 sealant (caulking) it probably would still leak to some degree.

      It is possible that a pipe in the wall is leaking and that is the source of the water coming through the ceiling. You should hire a plumbing leak expert to verify if the pipes are leaking.

      If there isn’t a pipe leaking then you should remove the tile floor to determine where the leaking and then properly waterproof it and re-install the tile. It might be necessary to replace the wall tile too since you might not have replacement tile for removing the bottom row of wall tile so the waterproof membrane can transition up the wall.

      If water is going through the ceiling then you will have to dry out the ceiling cavity or you can get, or do have, microbial growth going on inside the cavity that has been subjected to water.

  11. Jenny says:

    I would appreciate some expert advice… My shower is leaking behind the wall where the bottom right corner of the shower frame and wall meet, causing the discolouration on the wall due to moisture… I have had the wall tiles regrouted and the shower frame recaulked with silicone I think, however, the leak is still occurring slowly after the shower. I saw the water leaked through the weld from the shower frame so I put silicone on the weld to prevent the water seeping through and I am planning to replace the shower screen to stop the leaks. However, I can see the leak still occurring behind the wall after recaulking and regrouting so I am not sure if replacing the shower screen will help and whether the leak is caused by a plumbing issue. The leak doesn’t happen when the shower is not used. What should I do?

    • Donato Pompo says:

      If the water is leaking from behind the tiled wall, then the source of the water must be coming from behind the tile wall.

      Stopping the leak from the outside is only treating the problem, and not fixing the problem.

      It is possible that the leak could be coming from a pipe inside the wall. Since it only leaks when you use the shower then the leak has to be on the shower side of the water valves. There might be a loose pipe or an opening where water is getting behind the wall. I would hire a plumbing leak expert to see if he can detect where the leak is coming from.

  12. Francesca Pungitore says:

    I have a small tile crack pn my bathroom floor and the toilet is always full to the toilet rim when flushed. When every the toilet or bath tub or washing machine is in use, sinks are not blocked either, water leaks from the cracked tile.

    What can i do to stop this

    • Donato Pompo says:

      If the only time you see water coming through the cracks in your tile floor in the bathroom is when either the toilet, bath tub or washing machine is in use then I would think they only thing that those items have in common is the drain. So I would have a plumber inspect the drains to see if there is a leak and if there is any blockage.

      The blockage would cause the sewer water to back up, but there must be a breach in the sewer pipe to allow water to back up; unless the sewer water is coming from the toilet connection where the seal may be damaged.

  13. Smilealot says:

    Hi. We recently moved to a 35yr old house but the bathroom tile and kitchen tile are remodeled. But whenever I kid spills some water or if some water leaks i can see the water leaks in the basement ceiling right below the bathroom. It doesn’t feel good if it leaks like this even for a mug of water especially at the corner. How to fix it/ waterproof it?

    • Donato Pompo says:

      If water is leaking from the bathroom down to the ceiling of the basement then you do need to figure out why it is leaking. You could end up with collateral damage by the water causing degradation or microbial growth in the wood subfloor or within the floor cavity.

      First thing you need to do is determine where it is leaking at and then how is the water passing through the bathroom floor into the subfloor cavity and to the ceiling below. This can be tricky because the source of the leak may not be near where the water comes out as it may travel a ways.

      If the leak is a the perimeter of the bathroom and you can identify how it is leaking you might be able to simply remove and replace that area. Or it might be a bigger problem requiring the entire floor to be replaced. It all depends on how it was original installed and in what condition it is currently in.

  14. Elizabeth says:

    Very old (1930s?) fully tiled bathroom and shower with tile in concrete. When shower is used, one floor board on adjacent bedroom wall gets moist, not a lot, but overtime enough. Some tile grout has deteriorated and some hairline cracks. We do not want to demo bathroom. Should we regrout, seal transition joints with sealant and is there a clear coat to use over entire area?

    • Donato Pompo says:

      If water is leaking into another room through a wall when you use the shower then you have a serious leak. What getting into a wall cavity is likely to develop microbial growths (mold) that can be unhealthy. You need to determine where the water is leaking from and fit it, or if you can’t determine that then you need to replace at least the shower pan and transitions.

  15. Namita says:


    When I use shower, my granite tile wall soaks water and turn dark but in some of the tiles only just around the grout. This is in the wall away from where the shower head is installed. I had my granite sealed recently but this is still persisting. I am not sure if my grout is soaking the water and letting it go to the tile around it. Please let me know the remedy. Many thanks

    • Donato Pompo says:

      If you have a polished granite, normally it will not absorb moisture. There are other geological classifications of stone similar to granite that might have a higher absorption.

      Chances are that the water is migrating through the grout and into the sides of the stone. When you seal the granite tiles you should be sealing the grout. To verify that the grout or tile is sealed, spray a small amount of water on it. If it is adequately sealed, the water will roll off. If the grout turns dark then it is still absorbing moisture.

      Sealers normally don’t last that long and you have to reapply every 6 months to a year. Although there are some sealers that use a siloxane technology where supposedly the sealer develops crystalized matrix within the grout or tile that absorbs it. It is called Prosoco SURE KLEAN Weather Seal Natural Stone Treatments modified siloxane sealer. Normally it doesn’t benefit granite because it doesn’t absorb it, where the grout will absorb it. You can go to our website where there are a list of sealer manufacturers at

  16. Cathy Reese says:

    I had a very expensive shower put in a few months back. It is leaking onto the floor when I use it; the water is where the dam adjoins the bathroom floor. I believe it is leaking where the top or horizontal sureface of the dam meets the shower wall, which is also below where the hinges are for the glass shower door. I started exploring this issue and then realized that the very expensive tile guy apparently did not know that you do not grout a change of plane; you use silicone of some kind. So he did not seal any of the places where shower floor meets walls. He also did not seal where top of dam meets wall. I am hoping that if I use my (Latasil) sealant there, it may stop what I am assuming is seepage through that grout joint. Thoughts? Thank you—-Cathy R

    • Donato Pompo says:

      If I understand you correctly, the shower dam at the entrance of the shower that has a glass door is allowing water to leak out over the top of the dam onto the bathroom floor.

      Although all transitions of planes (i.e. where the top of the dam transitions to the shower door vertical door jams) should be filled with an ASTM C920 sealant (silicone or polyurethane caulking), the leak is not likely coming out of that transition joint if it is only filled with a porous cementitious grout.

      The leak is more likely due to the shower door not fitting properly to prevent water from leaking out. Either the wrong shower door was purchased or the shower door was not installed correctly. The person who installed the shower door should fix it.

      Although if the shower dam to door jam is not square because the tile installer did not install it correctly, that also could be why the shower door is leaking.

  17. No name says:

    I have a new house and there is a water leak through floor tile near drain but not close to drain .Builder is not accepting that there is any problem.The guy was saying it is normal and will dry up and will never come back if we don’t use shower for a week. We did not use shower for more than a month still the same. As per him this is normal. I don’t agree with it.My other showers don’t have that problem.
    My concern is why only through certain area and not the whole shower and not other showers. Not sure how to resolve the issue and don’t know what is the problem.

    • Donato Pompo says:

      Your builder’s statement does not make sense. A shower should never leak. If it leaks it isn’t going to fix itself. The leak is the symptom of the problem. The challenge is to determine the problem, which is where the water is coming from.

      For a tile shower that is likely to require removing some of the tile to see if the water is coming from a drain or is the water not draining beneath the tile because the drain weep holes are plugged and it is backing up and traveling through a breach in the waterproof membrane that should be under the tile on a presloped surface sloping towards the drain weep holes.

  18. Megan Enriquez says:

    Every time it rains heavily, 30cm puddle of water collects in the middle of the floor of our finished container shed. theres no leak from the roof whatsoever but there is a slight leak on the windowsill about 1 metre away. Its like the water just sucks up from the ground as there’s no trail from the sill to the puddle. We dont know how to fix it as we cant determine how it gets there

    • Donato Pompo says:

      30 cm is about 12 inches. That is a lot of water. You didn’t mention tile so I don’t know if this is a dirt floor or whatever…

      You could have a high water table so when it rains the water in the grout rises. After it stops raining the water table drops. You can dig french trench drains around the perimeter of your shed to diver the water. Although if there is too much volume of water then you need to install a sump pump to pump it out.

  19. Kelly Maree says:

    Hi there! Great article.. I was wondering if you could help me. I’ve noticed I have started to develop a wet patch on the carpet in the doorway to my ensuite opposite to where my shower is. When I lifted the carpet up there appears to be water coming from underneath the tiles. A wet patch doesn’t occur every time I use the shower, only sometimes. But when it does happen, it is after someone has had a shower. I looked at the floor in my shower, and it appears there is no longer any group left in most of the tiles. What should my next course of action be? Should is silicone around the edges of the shower? Can I use silicone instead of grout as I have no idea how to grout. Thank you!

    • Donato Pompo says:

      The water under the carpet is the symptom of the underlying problem. Treating the symptom normally does not fix the problem.

      The water is either coming from shower door or other transition to the outside or it is coming from under the tile. If it is coming from under the tile then chances are your waterproof membrane under the shower floor was not installed correctly. It may only leak after you have taken a certain length of shower.

      To figure out where the water is coming from in order to determine how to fix the problem it takes an expert like CTaSC to forensically investigate by removing some tiles under various conditions to look for evidence. This can be expensive and maybe it is better to renovate the shower floor; of course if the problem isn’t found then you could end up with the same problem again.

      Using silicone at the symptom of the problem doesn’t stop the water from coming out of the shower. It may just cause it to come out from an other location. The water has to be contained in the shower.

  20. James says:

    Hi Donato, great article and appreciate the detailed responses above. I seem to have a similar problem as some of the above but am curious on proper resolution. We have a bathtub with a shower that had some cracked grout when we moved in so I initially scraped the grout lines and re-grouted and it seemed to resolve any leaking to the basement below. The issue was not where the tub meets the tiles as is usually the case as that looks to be properly sealed, but instead was in the 2nd and 3rd horizontal grout lines up. The grout I replaced with has since cracked and doesn’t seem to be holding as I would expect and I can see is leaking pretty badly again through the ceiling in the basement. I noticed the first time I grouted that there didn’t seem to be any concrete board or really anything behind the tiles, so I’m not sure the grout has anything to hold too. I’m when looking up through my exposed basement ceiling I see that the floor boards and joists are fairly wet after a shower and there is a steady dripping while shower is in use. If I use a silicone caulk between the tiles instead of grout would that resolve as a temporary fix? I’m concerned with the amount of water there may be a much larger issue behind the wall and that this may need a full restoration/remodel? We plan to use a second shower curtain on the wall side as well to prevent any further leaking to the lower level.

    • Donato Pompo says:

      You have a serious problem if water is getting into the wall cavity and getting the wood and other materials wet. This is likely causing microbial growth, which is not healthy.

      You are trying to treat the system of your problem rather than fixing the problem. The problem is that the shower wall is not constructed and waterproof correctly. There should be a vapor barrier behind the tile wall that prevents water from getting into the wall cavity. The tile substrate should have a waterproof membrane over it and the transition joint to the bathtub should be caulked with an ASTM C920 sealant.

      The solution is to replace the tile installation as it can only get worst. As a temporary repair you could remove the grout in the tile and fill it with the ASTM C920 sealant. If done correctly, it will make the grout joints water tight.

Leave a Reply

Your email address will not be published. Required fields are marked *